Traditionally, displays present information in two dimensions. Images displayed by such displays are planar images that lack depth information. Because people observe the world in three-dimensions, there have been efforts to provide displays that can display objects in three-dimensions. For example, stereo displays convey depth information by displaying offset images that are displayed separately to the left and right eye. When an observer views these planar images they are combined in the brain to give a perception of depth. However, such systems are complex and require increased resolution and processor computation power to provide a realistic perception of the displayed objects.
Multi-component displays including multiple display screens in a stacked arrangement have been developed to display real depth. Each display screen may display its own image to provide visual depth due to the physical displacement of the display screens. For example, multi-display systems are disclosed in U.S. Patent Publication Nos. 2015/0323805 and 2016/0012630, the disclosures of which are both hereby incorporated herein by reference.
When a first and second displays or display layers are conventionally stacked on each other in a multi-display system, moire interference occurs. The moire interference is caused by interactions between the color filters within the layers when projected onto the viewer's retina. For example, when green color filters overlap, light is transmitted making for a comparative bright patch. When a green filter is over say a red filter, not as much light will be transmitted making for a dark region. Since the rear and front displays or display layers have slightly different sizes when projected onto the retina, the pixels will slowly change from being in phase to out of phase. This has the effect of producing dark and bright bands otherwise known as moire interference.
There have been several approaches to removing moire interference in a multi-layer display (MLD) system. Some approaches rely on removing unwanted frequency components by spatial filtering. This can be accomplished with either a diffuser type system whereby an element with a refractive index of about 1.5 has random surface perturbations, or a diffraction type system. The performance of these systems in terms of visual aesthetics (e.g., how blurry the image looks; how much residual moire is left; the effect on polarization; and cost, etc.) depend greatly on the system configuration. Certain MLD systems solely utilize diffusive optics to blur the rear-most display layer. This approach suffers from the following limitations: (a) the rear most image is inherently blurry—there is a trade-off between reducing moire interference and the clarity of the rear most image display layer; (b) the diffusing element utilizes a specialized diffuser pattern, which is difficult to obtain; (c) the diffusing element sits between polarizers and both the film substrate and stiffener substrate must be free of any birefringence; and (d) the diffusing element requires a separate stiffener component (usually glass) which adds weight and expense to the final display system. As a result, MLD systems using solely a diffuser to address moire issues do not provide an ideal solution to reducing moire interference, especially as those systems have reduced form factors.
Historic and present methodologies that rely only on diffusers to address moire interference do not provide an acceptable solution to the moiré issue without the introduction of significant and detrimental side-effects to image quality.
Certain example embodiments of the instant invention provide solution(s) that make moiré interference in MLD systems vanish or substantially vanish, but without significantly sacrificing the rear display resolution and contrast. In certain example embodiments of this invention, the MLD system includes first and second displays. Color filters of the first display are offset and/or differently arranged compared to color filters of the second display, in order to reduce or eliminate moire interference. In certain embodiments of this invention, color filters of the first display are arranged in a dissimilar manner compared to color filters of the second display, in order to reduce or eliminate moire interference. Dissimilar color filter arrangements according to this invention, on different displays of a MLD system, may or may not be used in combination with other moire reducing techniques (e.g., diffuser(s) and/or refractive element(s)) according to various embodiments of this invention.
In certain example embodiments of this invention, there is provided a display device comprising: a first display in a first plane for displaying a first image; a second display in a second plane for displaying a second image, wherein said first and second planes are approximately parallel to each other; and wherein the first and second displays have different color filter patterns, respectively, as viewed from a point of view of a viewer of the display device, in order to reduce moiré interference.